This application claims the benefit of the Korean Application No. P2000-85798 filed on Dec. 29, 2000, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a total reflection prism and a projector with the same.
2. Background of the Related Art
The projector enlarges, and projects a small picture by using a projection lens to a large sized screen, to display a large sized picture. The projector is provided with a color wheel for splitting a red color xe2x80x98Rxe2x80x99, a green color xe2x80x98Gxe2x80x99, and a blue color xe2x80x98Bxe2x80x99 on time basis for reproducing colors. The color wheel is rotated by motor for splitting the colors in succession. FIGS. 1 and 2 illustrate related art projectors.
Referring to FIGS. 1 and 2, the related art projector is provided with a lamp 1, a reflection plate 2, a color wheel 4, a rod lens 6, first lenses 7 and 8, a mirror 10, a second lens 12, a prism 16, a display 14, and a projection lens 18.
Beams of lights from the lamp 1 are focused onto the color wheel 4 by the reflection plate 2, and the color wheel 4 transmits the red, green, and blue colors in succession as motor 5 rotates the color wheel. The beams split by the color wheel 4 are incident on the rod lens 6, and the rod lens 6 makes the beams uniform for uniform distribution of the beams on a screen. The beams passed through the rod lens 6 proceeds to the mirror 10 through the first lenses 7 and 8, and reflected at the mirror 10 toward the second lens 12. The second lens 12 focuses the beams from the mirror 10 onto the prism 16, and the prism 16 guides the beams from the second lens 12 to a display 14, and, on the same time, supplies a picture beam from the display 14 toward the projection lens 18. The display 14 produces a picture beam loaded with picture information by using the beams from the prism 16. The prism 16 reflects the picture beam from the display 14 toward the projection lens 18. To do this, as shown in FIGS. 3A and 3B, the prism 16 has a first reflection surface 20 for reflecting the beams from the second lens to the display for the first time, and a second reflection surface 22 for reflecting the picture beam from the display 14 to the projection lens 18 for the second time. Finally, the projection lens 18 enlarges the picture beam, and projects the picture beam to a screen at a distance in front of the projection lens 18. FIGS. 4A and 4B illustrate related are the color wheel in FIG. 1.
Referring to FIGS. 4A, 4B and 5, the related art color wheel 4 is provided with color filters 26 each for transmitting a beam of light with a wavelength of a relevant color among the white beams, a coupler 24 having the color filters 26 fitted thereto, and a motor 5 having the coupler 24 fitted thereto.
The color filter 26 is provided with a red color filter 26R for transmitting red beams among the white beams, a green color filter 26G for transmitting green beams among the white beams, and a blue color filter 26B for transmitting blue beams among the white beams.
The color filter 26 is attached to the coupler 24 by an adhesive, and the coupler 24 is fastened to the motor 5 by holes 25 therein. That is, the color filter 26 splits colors in succession as the motor rotates the color filters 26. It is preferable that the beam passes a boundary 27 of the color filters within the shortest time period when the beam transmits the color wheel 4 shown in FIGS. 4A, 4B and 5. For an example, when it is assumed that the motor rotates at 3600 rpm for displaying 60 fields per a second, a time period required for the beam to pass the boundary will be calculated. In this instance, it is assumed that the beam is rectangular with an 8 mm width, and a 6 mm height, and the color filter 26 has an inside radius of 30 mm, and an outside radius of 40 mm.
Equation (1) expresses an angle when the beam passes a surface of the color filter 26, and the equation (2) expresses a time when the beam passes the boundary 27 of the color filter 26.                               θ          =                                    2              xc3x97                              arctan                ⁡                                  (                                      3                    31                                    )                                                      =                          11.055              ⁢              xc2x0                                      ,                            (        1        )            
(where, 31 is a distance from a center of the color wheel 4 to the beam, and 3 is a half of the height of the beam).                               t          =                                                    1                60                            xc3x97                              11.055                120                                      =                          1.54              ⁢                              xe2x80x83                            ⁢              μ              ⁢                              xe2x80x83                            ⁢              s                                      ,                            (        2        )            
(Where, 120 is a value obtained by dividing 360xc2x0 by 3, a number of boundaries 27).
From equation (2), it can be known that the time period required for the beam to pass through the boundary 27 of the color filter 26 is 1.54 xcexcs. As can be known from equations (1) and (2), for reducing the time period required for the beam to pass through the boundary 7 of the color filter 26, it is necessary to make the inside radius of the color wheel 4 greater. However, the greater the inside diameter of the color wheel 4, the larger and the heavier the projector become.
Moreover, the related art color wheel 4 can not be fitted overlapped with other optical system (various lenses), to require much space. Furthermore, the related art prism 16 makes two times of total reflection for transmission of the beams from the second lens 12 to the projection lens 18, with a loss of luminance.
Accordingly, the present invention is directed to a total reflection prism and a projector with the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a total reflection prism and a projector with the same, which permits to fabricate a thinner projector, and enhance a luminance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the total reflection mirror makes one time of total reflection of the beams of lights from an optical system to a projection lens.
In another aspect of the present invention, there is provided a projector with a total reflection prism including a light source for emitting beams of lights, a color wheel for receiving the beams from the light source, splitting color beams from the beams in succession, and transmitting the color beams, a transmission part for guiding the color beams to the prism, a display for producing a picture beam according to a video signal by using the color beams from the transmission part, a prism arranged between the transmission part and the display for guiding the color beams from the transmission part to the display, and reflecting the picture beam from the display, and a projection lens for enlarging, and projecting the picture beam.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.